Magnetic compass



C. H. COLVIN.

MAGNETIC COMPASS.

APPLlcArloN HLED luLv 19.1919.

1,334,273. l Patented Mar. 16, 1920.

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CHARLES H. COLVIN, 0F BROCKLYN, NEVI YORK.

MAGNETIC COMPASS.

Specification 0f Letters Patent Patented' Mar. 16, 1920.

Application led July 19, 1919. SerialNo. 311,960.

To all 107mm it may conce/m:

Be it known that'I, (l1-rennes H. Comin', a citizen of the `UnitedStates ot America,- residingl at Brooklyn, in the county of Kings andState of New York, have invented cel tain new and useful Improvements inMagn netic Compasses, ot which the following is a specieation.

This invention "relates to magnetic come passes. Particularly it relatesto Compasses for use in aircraft.

An object is to provide a compass which may be read either from the sideor trom the top and which may also be read trom either the back or thefront for obtaining the direction of Hight. A tui-ther object is toprovide a compass, the indicating means of which will appear magnified,making' it possible to read the compass with ineri'rased ease andaccuracy.

Another obJect ot this invention isl to provide a compass having astabilized rose.

or magnetic element lightlyA suspended in' a transparent container andfloated in liquid to damp out erratic action of the element; andv alsoto provide a compass rose or ele-- ment where the friction between thewalls of the container .and the element is reduced to a minimum.V

lWith these and other objects in view, the invention has relation to acombination and ,arrangement of Vcompass parts, an example of which isdescribed in the following speci iication, pointed out in the appendedclaims.

and illustrated in the accompanying' drawings, .vherein:

Figure 1 is a front or side view of the compass, as indicated b v theline 1-1 of Fig. 2. y

Fig. 2 is a top Viewo the compass. as indicated by the line 2-2-ot Fig.1.

Fig. 3 is a side view of the compass, as indicated by the lines 3-3 ot'Figs. 1 and 2. In this view the compass is shown in section, with theliquid removed.

A compass built accordingto the plans of this invention employs a liquidtype transparent bowl or container in which is 'floated and pivoted amagnetic element or compass rose. This element has a two-partdirectional indicating card lwhich may be read by the aviator eitherfrom thetop or sid'e, one part being a horizontal cardwith grada ations,and the other part being approximately vertical withgraduations. Eachcard claims.

.skilled in theV art.

is read, separately from the other, and there exists a certain relationbetween the graduations 'of the cards which characterize this invention,as depicted in Vthe appended Referring more 4particularly to` thedrawings, 2 points out a base upon which may be mounted one or morebackets 3 employed to hold the compass in service position on anairplane. The base is provided with an eX pansion diaphragm 4t otanyapproved type. The diaphragm is provided with a cover 7 fitted to thebase. rHoles are provided in the base to allow fluid movement relativelywith the diaphragm. This construction provides an expansion chamberwhich compen sates for liquid expansion due to temperature changes.` A.boss 8 isunade on Vthe 4cover and provided with tubular openings used tohold compensating magnets which are usually employed for correcting'deflection of the magnetic element.

A transparent tubular casing or bowl E) is Iitted to the base with atiattransparent cover or plate 10 placed on the top of the bowl. 'A gasketis interposed between the edge of the bowl and base to form a liquidtight joint therebetween. A' ring 11 is Iitted to the periphery oit thecover plate with suitable gaskets interposed 'between the ring,` andplate, and between the plateand edge of the bowl. Screws 12 are used todraw the ring and base together thus clamping the compass parts insecure relation. The compass bowl' is iilled with a suitable liquid.

A post 14 is iXed centrally to the-base, and a magnetic element pivotedon the upper end thereof in any approved manner by -usingan appropriatet'orm of pivot means betfween the element and post. The element may havea buoyant, characteristic which functions to lightly support it on thepost. The magnetic element? comprises the usual lioat and magnets asiswell cknown to those The element further con-A sists cfa horizontal card16 and a vertical card 15. Thecards are indexed to indicate direction,and may be marked on or attached for example, the mark N,

such a Way that the marks on the horizontal card 16 indicate thedirection which would be pointed out by a line drawn from the center ofthe card through the mark, and the marks on the vertical card 15indicate the direction which would-be -pointed out by a line drawn fromthe mark through the center of the card. That is, the markings on thetwo cards differ from each other by a halfv circle, or 180 degrees. Inviewing the lcompass from the side the pilot may read, and even thoughhe is reading this mark made on the south side of the card, he will takethe N mark as the direction on which the craft is headed. Thenin readingthe horizontal card he will read the N mark directly on the north side.

Lubber lines 17 and 18 are disposed in.

the bowl adjacent the rim of the magnetic element. These lubber linesare so arranged that a plane passed through them would alsopass throughthe center of the card, and' this plane or center line would point outthe direction in which the craft,-

upon which the compass is mounted, is headed or fiying. The directionof' this heading is then indicated by the mark on the vertical cardadjacent to lubber line 17 and by 'the mark on the horizontal cardadjacent to lubber line 18, assuming that the compass is being observedas in Fig. 1, or on the north side. The lubber line 18 and the card 16are observedthrough the transparent top of' the compass and the lubberline 17 and the card 15 are observed through the transparent sides ofthe compass, by an observer who is facing approximately in the directionin which the craft is heading. It.

`or tail of the craft however, the compass is observed from the otherside, as may be advantageous in aircraft, the direction pointed out bythe stern isvread through the top of' the compass by means of' thelubber line 17 and the card "16,01 through the sides of the compass bymeans oflubber line 18 and card 15. Being ableto read the compass fromeither the top or side, and from either the .front or back is one of theobjects of the invention herein disclosed, for it often happensthat morethan one person is observing the compass at the same time. For instancethe compass' may beso placed in anv aeroplane that the pilot willobserve it from the top while the navigator or observercwill read itfrom the side, or vice versa. Hence the advantage in a compasshaving atwopart card with the characteristic graduations,and transparentcontainer as described.

In observing the vertical card 15 through the transparent cylindricalsides of the compass, the card is seen greatly magnified in his isbecause vtant that lthe float shall receive a the transparentcylindrical sides, together with the liquid between the. sides and the,card, form a cylindrical lens.

In a compass used on aircraft it isnimpor- .minimum of disturbance, duetothe movements ot the craft, particularly the turning oit the craft.rl,`he movement ot the craft is transmitted to the compass bowl, whichcontains the liquid, but as the major portions of this bowl are made ota smooth transparent sub` stance such as glass, movement ot the bowl hasa minimum ol? frictional efl'ect on the liquid, and as the liquid isvery little distui-bed, the iioat is very little afiected by themovements of the aircraft. The compass therefore provides an adequateanddependable navigating instrument for all manner of craft, and is, strongand durable in con struction.

Having described my invention what I desire to patent and .secure byLettersy Patent is: A

1. A compass,l comprising in combination. a magnetic element having twocards, the graduations of which are opposite, that is: one c ardgraduated so that the marks on the card correspond to the directionwhich would be pointed out by a line drawn from the center of the cardthrough the mart, and the other card graduated so that the marks on thecard correspond to the direc tion which would be pointed out by a linedrawn from the mark to the center ot tln` card; the first named cardbeing in an approximately horizontal plane and adapted to be observedand read from above, and the second named card heilig in auapproximately vertical plane and adapted to be observed and` read fromthe side. i

2. A compass, comprising in combination.

a magnetic element having two cards, thegraduations of' which areoppositie, that is: one card graduated so that the marks on the cardcorrespond to the direction which would be pointed out by a line drawnfrom the center of the card through the mark, and the other cardgraduated so that the marks on the card correspond to the directionwhich would be pointed out by a line drawn from the Amark to the centerot the card: the first named card being in an approxi mately horizontalplane and adapted to be observed and read from above, and the secondnamed card being in anapproximatelv vertical plane and adapted to beobserved and read from the side; liquid surrounding

